In optical apparatuses or optical disc apparatuses, a movement mechanism capable of controlling the position of a lens with a high accuracy is used. The movement mechanism includes, for example, a stepping motor, a feed screw that is rotated by the stepping motor, and a rack that engages with the feed screw. A lens holder for holding a lens is connected to the rack. If this movement mechanism is used, the amount of movement of the lens in the optical axis direction can be controlled in accordance with the amount of rotation of the stepping motor. As a result, it becomes possible to realize accurate positioning of the lens.
In such movement mechanisms using a stepping motor, an operation called origin search needs to be performed for determining the reference of rotation of the stepping motor, every time the movement mechanism is started. In the origin search, the rack or the lens holder is pressed against a predetermined reference object (stopper or the like), and the state of the stepping motor as it is at this time is defined as a reference. When the operation of pressing has been performed, it sometimes happens that the feed screw is tightened up and goes into a bite-in state, and that the rack or the lens holder cannot be pulled back from the pressed position. In addition, also when a shock is given from the outside, the rack and the feed screw can go into a bite-in state.
Patent Literature 1 discloses a method in which, when a movement mechanism becomes unable to operate owing to an occurrence of a bite-in state, a drive torque of a stepping motor is increased and the direction of rotation of the stepping motor is inversed, whereby a rack is forced to move and the movement mechanism recovers from the bite-in state.